This invention relates to a submersible motor for driving an underground water pump and, in particular, to an assembly of these two units. A conventional motor driven device as shown in FIGS. 1 to 4 has a circular recess 700 along the lower side of a pump 200 between an end cover 180 mounted on the upper side of a motor 100 and a lower flange 211. The end cover 180 is provided to prevent undesirable particles, such as sand, from entering the area 170 of oil seals 171 and 172.
The end cover prevents comparatively large or heavy particles from entering the oil seal area 170 and consequently prevents wear on the oil seals 171, 172 and motor shaft 160, due to the entry of such large particles into the gaps between the oil seals 171, 172 and the motor shaft 160 while the motor 100 is operating.
During the operation of the motor pump, comparatively small or light weight particles are continually sucked in along with liquid, and flow out again from the area of the suction frame 210 of the pump towards the vanes thereof. It is unlikely that such undesirable small particles enter the oil seal area 170 through the gap 181 between the end cover 180 and the motor shaft 160 when the pump 200 is operating.
After being submerged, the motor and pump have periods of continuous operation as well as periods of inactivity, when pumping is not required. During these periods of inactivity of the motor pump, the small particles, which were sucked in and float in the liquid during operation, fall, by gravity, into and accumulate within the space or recess 700. Some of these undesirable small particles then fall into the oil seal area 170 through the gap 181 between the end cover 180 and the motor shaft 160, and from there, proceed to enter a small gap between the oil seals 171, 172 and the motor shaft 160.
This tendency is particularly prevealent in the case of industrial pump motors, that is, motors used in pumping a liquid containing a comparatively large number of particles. With such tendency, it is preferable to employ a disc-like collar attached to the motor shaft at a position over the end cover to prevent undesirable particles from falling into the oil seal area. As a result, a collared prior art motor shown in FIGS. 5 and 6 is sometimes utilized to combat this problem in industrial use.
Although the collar 190 shown in FIGS. 5 and 6 may indeed prevent undesirable small particles, such as sand, etc., from falling directly into the gap between the end cover 180 and the motor shaft 160, it can not, however, prevent another occurrence which is explained as follows. If the period of inactivity is long and a large volume of undesirable particles is contained in the intake liquid, a large percentage of the particles fall into and accumulate within the space or circular recess 700 between the collar 190 and the end cover 180 and the lower ring flange 211 of the pump 200.
These accumulated particles in the circular recess 700 are contained by and movable in the liquid. Therefore, their relative position will change. As a large volume of particles accumulates in the recess 700, they move into the gap between the collar 190 and the end cover 180, and on into the area 170 of the oil seals 171, 172 through the gap between the end cover 180 and the motor shaft 160. During long periods of inactivity, the weight of the large volume of accumulated particles in the circular groove 700 itself causes the particles to shift in between the oil seals 171, 172 and the motor shaft 160, causing undesirable wear.
More specifically, when the motor begins to operate the liquid bearing the particles accumulated within the circular recess 700 and the gap between the collar 190 and the end cover 180 moves freely within these areas. This free motion enables the particles and liquid within the circular groove 700 and the gap between the collar 190 and the end cover 180 to move into the area of the oil seals 171, 172, as well as causing the undesirable wear of the oil seals 171, 172 and the motor shaft 160.
It is desirable, therefore, to prevent the abovementioned tendency, which has until recently gone undiscovered.